# Super HARD C3 question.

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#1
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5 years ago
#2
(Original post by hajs)
Are you sure this is C3? It is easily provable (took some thinking) with the tan compound angle formula, but I don't know how to solve this in C3 terms (then again, I don't know the spec and compound angles could be in C3). Also, it is definitely correct - check with a calculator - I just can't think how to prove it otherwise which is kinda bothering me :/
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#3
(Original post by Duskstar)
Are you sure this is C3? It is easily provable (took some thinking) with the tan compound angle formula, but I don't know how to solve this in C3 terms (then again, I don't know the spec and compound angles could be in C3). Also, it is definitely correct - check with a calculator - I just can't think how to prove it otherwise which is kinda bothering me :/
Yes its definitely C3. Shall i send the answer? Maybe that can help to explain it..??
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#4
(Original post by Duskstar)
Are you sure this is C3? It is easily provable (took some thinking) with the tan compound angle formula, but I don't know how to solve this in C3 terms (then again, I don't know the spec and compound angles could be in C3). Also, it is definitely correct - check with a calculator - I just can't think how to prove it otherwise which is kinda bothering me :/
Just googled it, yes it is that formula, never heard of it before.. care to explain?
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5 years ago
#5
(Original post by hajs)
Yes its definitely C3. Shall i send the answer? Maybe that can help to explain it..??
Yes, that would help explain it (I want to know now too :P )

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#6
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5 years ago
#7
(Original post by hajs)
That uses the compound angle formula but without saying it is. I don't remember being taught that as just a standalone rule so I'm guessing you were expected to know the compound angle formulae :/

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#8
(Original post by Duskstar)
That uses the compound angle formula but without saying it is. I don't remember being taught that as just a standalone rule so I'm guessing you were expected to know the compound angle formulae :/

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So is it not C3? It came up in one of the C3 elmwood papers in doing.. Is it further maths or something

Can you still explain it to me..
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5 years ago
#9
(Original post by hajs)
So is it not C3? It came up in one of the C3 elmwood papers in doing.. Is it further maths or something

Can you still explain it to me..
I guess it's a case of different boards - I do OCR MEI and I'm pretty sure we don't do compound angles until C4. Regardless, here's a page with all the formulae on

The one used here is the forumla for tan(a - b), because the gradient is equal to the tan of the angle that the gradient makes with the x axis, and the angle between the two is the larger (a) minus the smaller (b). In this case, tana = 1, and tanb = 1/3. The second line of the answer is the substitution of those values into the expansion for tan(a - b) which is on the website I linked. This leaves you with a value for tan theta and then you can take atan of both sides and qed.
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5 years ago
#10
(Original post by hajs)
x
(Original post by Duskstar)
x
The angle between two lines of gradients is given by:

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5 years ago
#11
(Original post by lizard54142)
The angle between two lines of gradients is given by:

But that's literally an abstraction of the tan double angle formula. Are there any exam boards which have that on the spec then?
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5 years ago
#12
(Original post by Duskstar)
But that's literally an abstraction of the tan double angle formula. Are there any exam boards which have that on the spec then?
I'm not sure to be honest. It's a pretty standard result.
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5 years ago
#13
(Original post by hajs)
it is nice to be able to do this (all mathematicians to be should be able to do this)
but this is NOT in the C3 specification of any board...
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5 years ago
#14
Where is this question from?
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5 years ago
#15
(Original post by Super199)
Where is this question from?
an Emwood paper ...
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5 years ago
#16
(Original post by TeeEm)
an Emwood paper ...
Are the papers any good?
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5 years ago
#17
(Original post by Super199)
Are the papers any good?
I could not possibly comment on a public forum ...
0
5 years ago
#18
I've heard IYGB papers are good. Solomon, Elmwood etc. all wish they could be as good as IYGB.

Spoiler:
Show
TeeEm, when do I get paid?
3
5 years ago
#19
(Original post by notnek)
I've heard IYGB papers are good. Solomon, Elmwood etc. all wish they could be as good as IYGB.

Spoiler:
Show
TeeEm, when do I get paid?
I will give you 50% of what I earn from them ...
0
5 years ago
#20
(Original post by TeeEm)
I will give you 50% of what I earn from them ...
Next year I'm not going to do weekly problem sheets.

Instead I will opt to hand in worked solutions to TeeEm's undergrad questions.

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